So I'm thinking of running an "A Song of Ice and Fire" game using Green Ronin's system. If your not familiar with ASoIaF or Game of Thrones, the basic idea is low-magic fantasy setting, kind of a crapsack world controlled by seven competing 'kingdoms'.

My idea for the game is that the players will create and take control of one of the minor noble houses in this world, and compete, scheme, and ally with one another to pursue the goals that the players set for themselves, with myself acting less as a GM and more as a 'referee'.

However, I'm wondering if I'm setting myself up for failure by allowing / encouraging player conflict. Has anyone else ever run a game like this before? Any tips / ideas on how to make it work? Or is this idea doomed from the start?

I wouldn't say so. As long as your players are good sports, you've got some decent rules laid down about the nature of the competition, and everyone stays civil, player competition can generate a lot of fun.

Yeah, I've run this kind of game before. It worked really well, actually, since all of the players know what they are signing up for, I didn't see anyone get their feelings hurt. The only thing that killed games was player attrition.